Changes in the ENSO-AZM connection under global warming

El Niño-Southern Oscillation (ENSO) affects weather and climate around the world but its impact on the equatorial Atlantic has been surprisingly inconsistent, with some major El Niño events followed by cooling in the equatorial Atlantic, while others were followed by warming. Here we use climate change projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to examine how ENSO’s relation with the equatorial Atlantic may change under global warming.Similar to ENSO, variability in the equatorial Atlantic, also known as the Atlantic Zonal Mode (AZM), is influenced by the Bjerknes feedback, in which sea-surface temperature (SST) anomalies drive deep convection and a surface wind response that amplifies the original SST anomalies. Due to the stabilization of the atmosphere under global warming, this Atlantic feedback weakens in the CMIP6 projections. Instead, many models suggest a scenario in which the AZM is dominantly driven by ENSO’s thermodynamic forcing, namely the tropics-wide tropospheric warming (cooling) that follows El Niño (La Niña) events. As a result, ocean dynamics and coupled air-sea feedbacks play a much weaker role, while ENSO’s influence on the AZM becomes more consistent. Analysis with a simple linear prediction scheme suggests that this can also increase the predictability of the AZM, due to the high predictability of ENSO.While many models envision an ENSO-dominated future, some continue to simulate an independent, dynamically driven AZM until the end of the 21st century. The potential reasons for this disparate behavior will be discussed.